Returns the parent and child term slugs separated by a slash `parent-slug/child-slug`

gistfile1.sql

SELECT CONCAT(parents.parent_slug, '/', children.slug) AS slug 
FROM 
(
SELECT distinct t.term_id ,t.slug AS parent_slug 
FROM wp_term_taxonomy AS tt 
INNER JOIN wp_terms AS t 
ON tt.parent = t.term_id
) parents
INNER JOIN
(
SELECT t.slug, tt.term_id, tt.parent
FROM wp_term_taxonomy AS tt
INNER JOIN wp_terms AS t
ON tt.term_id = t.term_id
) children
ON parents.term_id = children.parent